Continuous web cutters are known in the art. Typically, a continuous web cutter is used to cut a continuous web of material into cut sheets, and provide the cut sheets to a sheet accumulator, where the accumulated sheets are moved to an insertion station in a mass mailing inserting system. In a typical web cutter, a continuous web of material with sprocket holes on both side of the web is fed from a fanfold stack into the web cutter. The web cutter has a tractor with pins or a pair of moving belts with sprockets to move the web toward a guillotine cutting module for cutting the web cross-wise into separate sheets. Perforations are provided on each side of the web so that the sprocket hole sections of the web can be removed from the sheets prior to moving the cut sheets to other components of the mailing inserting system. In particular, some continuous web cutters are used to feed two webs of material linked by a center perforation. In the cutter, a splitter is used to split the linked webs into two separate web portions before the linked webs are simultaneously cut by the cutting module into two cut sheets.
In a feed cycle, the paper is advanced past the blade of the guillotine cutting module by a distance equal to the length of the cut sheet and is stopped. In a cut cycle, the blade lowers to shear off the sheet of paper, and then withdraws from the paper. As soon as the blade withdraws from the paper path, the next feed cycle begins. The feed and cut cycles are carried out in such an alternate fashion over the entire operation.
In some web cutters, it is desirable to achieve a cutting rate of 25,000 cuts per hour or more, for example. This means that the web cutter has a feed/cut cycle of 144 ms. Typically the length of the cut sheet is 11 inches (27.94 cm). If the time to complete a cut cycle is about 34 ms, then the total time in a feed cycle is 110 ms. This means that the web must be accelerated from a stop position to a predetermined velocity and then decelerated in order to stop again within 110 ms. The acceleration and deceleration action of the tractor causes the paper web immediately upstream of the tractor to whip up and down uncontrollably. If the whipping motion is severe, the web may break. As the cutting rate increases, the problem becomes more acute.
Lorenzo (U.S. Pat. No. 5,768,959) discloses a web cutter wherein two separate modules are used to take in a web from upstream: a slitter module for slitting the web into two web portions so as to allow a cutter module to separately cut the web portions into sheets. In order to coordinate the movement of the web portions between the slitter module and the cutter module, two parallel paper loops are provided between the two modules.
While this approach helps reduce the breakage of the web, the loops are too large. Moving such a large loop might still cause the web to tear because of the inertia and whip when the web cutter operates at a high cutting rate.
It is advantageous and desirable to provide a method and device for further reducing the whipping motion of the web paper immediately upstream of the tractor and the tension in the web due to acceleration of the tractor so as to avoid breakage of the web.